1. Field of the Invention
The present invention relates to a susceptor, a semiconductor manufacturing apparatus, and a semiconductor manufacturing method which are used to supply a reaction gas to a front surface of, for example, a semiconductor wafer while heating the semiconductor wafer from a rear surface thereof to perform film formation and which are to hold the semiconductor wafer.
2. Related Art
In general, in a CVD (Chemical Vapor Deposition) apparatus used in formation of an epitaxial film in semiconductor manufacturing steps, a heat source and a rotating mechanism are arranged under a wafer, and a rear-surface heating method which can supply a uniform process gas from the top is used.
In recent years, with miniaturization and advance in function of a semiconductor device, a high level of prevention of metal contamination in a film forming step is required. In the above rear-surface heating method, the heat source and the rotating mechanism are arranged under the wafer, and the heat source and the rotating mechanism are not completely separated from each other. Therefore, the wafer is disadvantageously contaminated by diffusion and movement of metal atoms.
In general, a wafer is held by a susceptor in a deposition apparatus (reaction chamber) and moved upward by a push-up pin penetrating a pin hole formed in the susceptor in conveyance. Therefore, the wafer cannot be easily blocked from being contaminated, in particular, through the pin hole.
On the other hand, for example, in Published Unexamined Japanese Patent Application Publication No. 2000-43302 (JP-A-2000-43302), in order to try to make a wafer temperature distribution uniform, a susceptor having a structure in which no pin hole is formed is proposed. However, when the susceptor structure which is free from a pin hole is actually used, a gas-phase layer is formed under the wafer when the wafer is to be placed, and the wafer is floated. Therefore, the wafer cannot be stably held. Furthermore, when film formation is performed by heating and rotating the wafer and supplying a process gas, uniform film formation is difficult in such an unstable state. In order to perform uniform film formation, the wafer may deviate from a susceptor placing position in high-speed rotation, and uniform film formation by the high-speed rotation is disadvantageously difficult.
As described above, when the susceptor structure which is free from a pin hole is employed to block the wafer from being contaminated through a pin hole formed in the susceptor, it is disadvantageously difficult that uniform film formation is performed while stably holding the wafer.
The present inventors previously proposes a susceptor, a semiconductor manufacturing apparatus, and a semiconductor manufacturing method which suppresses metal contamination in the film forming step, can uniformly form a film on a wafer, can suppress a yield from decreasing, and can improve the reliability of a semiconductor device (Japanese Patent Application No. 2007-235685 (JP2007-235685) is incorporated) Note that JP 2007-235685 does not have been disclosed.
A susceptor structure of the above undisclosed previous application (JP 2007-235685) includes: an inner susceptor having a size smaller than a diameter of a wafer and a surface on which a convex portion to place the wafer is formed; and an outer susceptor having a first step portion having an opening at the center to place the inner susceptor to block the opening and a second step portion formed on an upper stage of the first step portion to place the wafer.
A semiconductor manufacturing apparatus of the above undisclosed previous application (JP 2007-235685) includes: a reaction chamber into which a wafer is conveyed; a gas supply mechanism to supply a process gas into the reaction chamber; a gas exhausting mechanism to exhaust the process gas from the reaction chamber; an inner susceptor having a size smaller than a diameter of the wafer and a surface on which a convex portion to place the wafer is formed; an outer susceptor having a first step portion having an opening at the center to place the inner susceptor to block the opening and a second step portion formed on an upper stage of the first step portion to place the wafer; a heater to heat the wafer from lower portions of the inner susceptor and the outer susceptor; a rotating mechanism to rotate the wafer; and a push-up pin which penetrates the heater to vertically move the inner susceptor.
In the susceptor and the semiconductor manufacturing apparatus of the above undisclosed previous application (JP 2007-235685), metal contamination in the film forming step can be suppressed while temperature control is not sufficiently performed, and a fluctuation in thickness of a formed film is generated.